I work in Illustrator all the time and I ask my self why or how can I snap a line or a shape to the tangent of another shape like Autodesk AutoCAD's "Tangent Constraint", some say that I can start with the Line Segment tool and go from there building the shape, but this option will give me a limited movement and it's not practical like if we have a tangent constraint in Illustrator so we can build logos and shapes more easier and that will make illustrator go to perfection more and more.